'That '70s Show' Star Lisa Robin Kelly Dead at 43

Lisa Robin Kelly poses on a film lot in Beverly Hills, Calif., April 12, 2000.

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Lisa Robin Kelly, best known for playing Laurie Forman on the sitcom "That '70s Show," died Wednesday at age 43, her agent told ABC News station KABC in Los Angeles.

The cause of death was unknown.

Earlier this week, Kelly, who struggled with addiction, checked into a rehab facility "where she was battling the addiction problems that have plagued her these past few years," her agent, Craig Wyckoff, said in a statement. "I spoke to her on Monday and she was hopeful and confident, looking forward to putting this part of her life behind her."

After making appearances on "Married With Children" and "Charmed," the Connecticut native landed her biggest role, the older sister of Topher Grace's character, Eric Forman, on the Fox series, "That '70s Show." She appeared on the sitcom from 1998 to 2003, according to IMDB.com, before she was replaced.

She later admitted to ABC News that she had a drinking problem at the time.

Kelly had many run-ins with the law in recent years. In 2010, she was arrested for driving while intoxicated and pleaded guilty. Two years later, she was arrested and charged with domestic violence after a fight with her ex-boyfriend John Michas. She denied the charge, and said that she was the one who had been assaulted.

Last spring, she told ABC News that she had been sober for three months and was eyeing a comeback.

"I am not running from this," Kelly said. "I have paid my dues and if I can make it through this I can make it through anything."

However, a few months later, she was reportedly arrested for assault and, in June, she was arrested again on suspicion of driving while intoxicated.